Increasing fuel costs have led to the investigation of numerous techniques for efficient utilization of solar radiant energy. There is increased interest, for example, in designing south-facing walls of homes and other buildings with large expenses of glass to capture the incident solar radiation for warming the interior of the building in the winter, and with appropriately placed overhangs to shield those windows from impingement of solar radiation during the summer. If standard glazing is used in such designs, however, it is no unusual to experience excessively high temperatures within the room on bright winter days. Thus, the solar radiant energy is not used to maximum advantage or with maximum efficiency.